The work, carried out together with collaborators at ICMAB led by Prof. Jordi Arbiol, indicates that the presence of water modifies the reactivity on the nanoparticle surface favoring the formation of the hollow structure. The paper also presents detailed characterization, including the magnetic properties of some of the products. Overall, the work contributes to the understanding and control of the chemistry of hollow nanoparticles – a topic of growing interest due to their potential applications.

Varón, M., Ojea-Jimenez, I., Arbiol, J., Balcells, L., Martínez, B., & Puntes, V. F. Spontaneous formation of hollow cobalt oxide nanoparticles by the Kirkendall effect at room temperature at the water–air interface. Nanoscale, 5(6), 2429–2436 (2013).

http://pubs.rsc.org/en/content/articlelanding/2013/nr/c2nr32657d

The paper presents the results on the use of electron holography to study 1D and 2D self-assemblies of magnetic (Cobalt) nanoparticles. The work reveals the correlation between particle arrangement and magnetic order, leading to the conclusion that ferromagnetism exists in these structures even in the absence of underlying crystallinity. This contributes not only to elucidating mechanisms at the nanoscale, but also to the application of nanoparticle assemblies in magnetic devices such as memories and sensors.

Varón, M., Beleggia, M., Kasama, T., Harrison, R. J., Dunin-Borkowski, R. E., Puntes, V. F., Frandsen, C. (2013). Dipolar Magnetism in Ordered and Disordered Low-Dimensional Nanoparticle Assemblies. Sci. Rep., 3.

http://www.nature.com/srep/2013/130206/srep01234/full/srep01234.html

(open access)

This workshop is meant to disseminate the scientific results achieved within the last 42 months by the EU-FP7 project MAGNIFYCO, on the topic: Magnetic nano-containers for combined hyperthermia and controlled drug release. Additionally, it includes the presence of external high level keynote and invited speakers working in closely related topics, such as Nanomaterials, Physical & Chemical Characterization, Functionalization, Diagnosis, Targeting and Hyperthermia.

The workshop will take place February 20-22 in Barcelona, in the Aula Magna “Enric Casassas” of the School of Chemistry and Physics, Universitat de Barcelona (Avinguda Diagonal 645, 08028 Barcelona). More information can be found at: http://www.magnifyco.eu/magnifyco-2013-workshop.

You are all invited to attend! (registration is free, till February 5, 2013).

Below follows the abstract of Víctor’s talk.

Inserting inorganic nanoparticles (NPs) into biological media is quite challenging. Specially if those NPs are supposed to perform a certain task in a certain moment. First of all there are aspects of simple aggregation, determined by density, size, concentration, media and surface state. Inorganic NPs are happy at low concentrations in low electrolyte concentration to have use of their high surface charge to overcome the handicaps of their high density and compactness. Besides, their biological counterparts are happy at high concentration in high saline media. This is regarding its colloidal stability, but NPs also suffer chemical and biological transformations as those of dissolution, corrosion, oxidation, or those corresponding with interactions with the immune system and phagocytosis. This is because inorganic NPs are normally unstable, that is why they are so active and interesting… such a high electronic density in the size of a protein! To illustrate that, look at a simple consequence of size: nanocarriers can strongly contribute to modifications in pharmacokinetics and biodistribution of the carrier drugs, by leading them through different pathways depending on the morphological, physical and chemical properties of the nanocarrier, which is especially appealing in the case of very toxic drugs. Inside the body, pores smaller than 1 nm have been only reported in the tight junctions on certain continuous capillaries (including the central nervous system, i.e., blood-brain barrier, placenta and testis barrier) while continuous capillaries (muscle, lung, skin) have pores of 6 nm. Fenestrated capillaries (kidney, intestine, some endocrine and exocrine glands) have pores up to 50–60 nm, usually closed by a diaphragm. Finally, discontinuous capillaries (liver, spleen, bone marrow) have pores between 100–1000 nm, which allow the passage of macromolecules between plasma and interstitium. Thus, small molecules (below 6 nm, the majority of drugs) leak in and out from the blood vessels and are rapidly (in minutes) cleared from blood via the kidneys while the passive transport of macromolecules through these porous is negligible. Thus a NP sized between 6–40 nm may follow protein paths to finally accumulate in organs of the mononuclear phagocyte system, especially the liver and spleen, as do proteins and protein aggregates, while larger sizes of NP are easily recognized by the immune system and also end up in liver and spleen but within a shorter time, all in all offering different paths to nanoparticles to tour. It is worth noting here that blood vessel permeability changes in diseases such as inflammation and cancer. All this aspects refer to morphological and intrinsic properties designed at the synthesis time to carefully choose composition, shape and size.